Proceedings Volume 7205

Advanced Fabrication Technologies for Micro/Nano Optics and Photonics II

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Proceedings Volume 7205

Advanced Fabrication Technologies for Micro/Nano Optics and Photonics II

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Volume Details

Date Published: 6 February 2009
Contents: 12 Sessions, 30 Papers, 0 Presentations
Conference: SPIE MOEMS-MEMS: Micro- and Nanofabrication 2009
Volume Number: 7205

Table of Contents

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Table of Contents

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  • Front Matter: Volume 7205
  • Nanofabrication I: Photonic Nanostructures
  • Biologically Inspired Nanofabrication
  • Micro- and Nano-Etching
  • Nanofabrication II: Growth and Deposition
  • 3-D Nanofabrication
  • Applications
  • Nanofabrication III: Metallic Nanostructures and Plasmonics
  • Micro- and Nanoreplication
  • Advanced Lithography
  • Laser-based Fabrication for Photonics
  • Poster Session
Front Matter: Volume 7205
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Front Matter: Volume 7205
This PDF file contains the front matter associated with SPIE Proceedings Volume 7205, including the Title Page, Copyright information, Table of Contents, and Conference Committee listing.
Nanofabrication I: Photonic Nanostructures
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Wire-grid polarizer for the UV spectral region
Thomas Weber, Hans-Jörg Fuchs, Holger Schmidt, et al.
In this work we present a metal wire grid polarizer for the UV spectral region. The period of the aluminum grating is 100 nm. The grating was fabricated using a spatial frequency doubling technique. The process consist of electron-beamlithography, sputter coating and various ion-beam- and ICP etching steps. The features of the fabricated aluminum wires fulfill the theoretical demands with a height of 150 nm and a width of 35 nm. Optical parameters of the grating at 250 nm wavelength are 42% transmittance and an extinction ratio of almost 15. The optical parameters are even improved with the wavelength.
Two-dimensional photonic crystal polarization filter with dual-band and wide working wavelength range
A novel design of photonic-crystal polarization filter was demonstrated with dual-band and wide working wavelength range. The structure of the filter is a 2-dimensional wavy structure of multilayer thin films consisted with a number of alternate high and low refractive indices transparent dielectric layers deposited sequentially on a periodic structured substrate. The fabrication of the photonic-crystal polarization filter is based on an autocloning method which integrated the techniques of lithography and thin film deposition. Different from the traditional polarizing beam splitters, the photonic-crystal polarization filter is a flat type of polarizer with normal incident angle. The transmission and reflectance spectra were analyzed using finite-difference time-domain method (FDTD). From the analysis result, we found the photonic bandgap was happened at transverse electric (TE) mode and the passband at transverse magnetic (TM) mode. So, the photonic crystal polarization filter can separate TE mode and TM mode effectively as the field is incident normally. We design the working wavelength range of the photonic-crystal polarization filter at both visible and near infrared regions, and have wide polarization separated band at normal incident. Finally, the bandwidth is about 100 nm in visible region and 300 nm at near infrared region. The extension ratio is about 20 both in visible region and near infrared region.
Biologically Inspired Nanofabrication
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Reproduction, mass production, and control of the Morpho butterfly's blue
Akira Saito, Yusuke Miyamura, Yoko Ishikawa, et al.
Strucural color of some blue Morpho butterflies has a physically mysterious feature, because it has both high reflectivity (>60%) and a single color in too wide angular range (>±40° from the normal), which are contradicting with each other from viewpoint of the interference phenomena. We have recently proven the principle of the mystery by extracting the physical essence, and emulating the nano-structures using nano-fabrication techniques. The key was exquisite combination of regular and random structures at nanometer scale. Such artificial structural color was found to concern wide applications, because the Morpho-color can produce a single color without pigment in wide angular range with high reflectivity. Also it makes colors impossible by pigment, and is resistant to fading due to chemical change over longtime. However, we must overcome several "death valleys" for wide industrial applications. A serious problem was low throughput in the fabrication process of nano-patterning by the conventional lithography, which was solved by use of nano-imprinting technique. Next research step is attempts at a precise control of the optical properties, in both terms of real space and wavelength, i.e. angular distribution and spectrum. We could successfully optimize the optical properties by controlling the parameters of nano-structures in the artificial film. In this process, optical simulations and micro-structural observations were taken in account. The optimization was achieved both theoretically and empirically by comparing a series of films fabricated with different nano-patterns. Also the relationship between the structural parameters and the optical properties was analyzed. The reflective characteristics of the optimized film were found to reproduce the optical properties closer to the natural Morpho-blue than the prototypes.
Replication of biotemplates for the development of highly efficient biomimetic optical metamaterials and devices
Biomimetics involves the implementation of ideas and concepts from nature in different technoscientific fields. Aiming at the further development of biomimetic optical metamaterials and devices, we devised the conformal-evaporated-filmby- rotation (CEFR) technique to fabricate inorganic replicas of biotemplates with high reliability and fidelity at the micro- and nano-scales. Some potential applications include high-sensitivity chemical sensors and biosensors, textured coatings for solar cells and other energy-harvesting structures, environmental sensors, high-speed motion detectors, surveillance systems, cameras for image-guided surgeries, as well as for many clinical treatments that can be controlled by implanted light-delivery devices. Moreover, we demonstrated the successful conformal coating of the external surface of a MEMS comb resonator by the CEFR technique, thereby extending application to microelectronics.
Spectroscopy nanofabrication and biophotonics
Gobind Das, Francesco De Angelis, Maria Laura Coluccio, et al.
This paper reports on the fabrication of reproducible surface enhanced Raman scattering (SERS) device based on nanoPillar coupled with PC cavity by means of FIB milling and electron beam induced deposition techniques (Device 1): In addition to this device, another SERS device using e-beam lithography and electroless metal deposition techniques (Device 2) is fabricated in order to have planar geometry particularly useful for future nanoarray architectures SERS device. Various measurements have been performed for the monolayer of different materials showing extremely promising SERS based device. It is revealed that the Rhodamine6G is clearly evidenced in Raman 2D mapping spectrum, showing a very high enhancement in SERS signal in the order of 1012 (theoretically) with respect to the normal Raman measurements. We estimate the number of Rhodamine6G molecule detected is about 100-150.
Micro- and Nano-Etching
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Sub-100-nm pattern transfer on compound semiconductor using sol-gel-based TiO2 resist
Boyang Liu, Seng-Tiong Ho
The possibility to pattern III-V compound semiconductor with nanometer scale is of great interest to photonic, electronic and optoelectronic systems. Typical method for sub-micrometer compound semiconductor dry etching utilizes PMMA or other resist to transfer patterns to SiO2 as intermediate masks due to resist's low etching selectivity, especially for ultra-small features. This additional pattern transfer will inevitably increase the potential damage caused by plasma dry etching and the complexity of patterning process. Therefore, it is desirable to find an easier and more effective way to pattern compound semiconductor. In this paper, we report a new approach of direct pattern transfer using Ti(OBun)4 solgel derived TiO2 resist as mask. The optimal dose of TiO2 resist for e-beam lithography is ~220mC/cm2. Thermal stability study of spin-coated TiO2 shows a good performance as lithography resist even at 300°C, which will have wider applications than conventional resists. Post-annealings at different temperatures are performed to study temperature-dependence of patterned TiO2 resist as dry-etching mask. The etching selectivity of sample InP compound semiconductor to TiO2 resist is over 7:1. A variety of sub-100 dry etching patterns with good profile qualities have been obtained. The aspect ratio of etching patterns is over 20:1, and the smallest feature is as small as 20nm with over 600nm deep. This sol-gel derived TiO2 sipn-coatable nanolithography resist with high etching selectivity and high aspect ratio etching profile provides a novel and convenient way to directly pattern compound semiconductor material for various challenging nano sacle photonic, electronic and optoelectronic applications.
Vapor phase release of silicon nanostructures for optomechanics application
Suspended silicon based nanostructures for optomechanic applications have been successfully fabricated using the Hydrofluoric acid (HF) vapor phase etching technique. In this paper, we demonstrate the fabrication of parallel silicon waveguides with a cross section of 250nm x 220nm, and photonic crystal nanobeam cavities with an air gap as small as 50nm between these released structures. The waveguides have been suspended over a distance of more than 75um. Stiction is a major issue for releasing structures with gaps in the order of tens of nanometers. At the same time, the process has to be gentle due to the small dimensions of the structures involved in the release process. HF vapor etching technique was successfully utilized to etch the 2um thick thermally grown sacrificial silicon oxide layer. This process has an high yield as no liquid is in contact with the structures being released, thus eliminating any kind of liquid flow which typically proves to be a potential destruction source for such small structures. This HF vapor phase etching is a simple and controllable process which completely eliminates the requirement of any kind of sophisticated drying techniques needed with conventional wet etching.
Shallow Fresnel lens fabrication using grayscale lithography made by high energy beam sensitive mask (HEBS) technology and reactive ion etching
Tali Nachmias, Avi Ohayon, Shefer E. Meltzer, et al.
We describe the fabrication and the characterization of high efficiency Fresnel lenses by the use of gray scale lithography (GSL), followed by reactive ion etching (RIE) or deep reactive ion etching (DRIE) to transfer the pattern from the gray scale resist into the silicon substrate. Three versions of Fresnel lenses were fabricated, with height of 600nm, 1800nm and 5500nm. The desired lens height in silicon is determined from photoresist height and the selectivity of the etching process. A low selectivity DRIE process was developed in order to fabricated 1800nm and 5500nm Fresnel lenses. The 600nm Fresnel lens was fabricated using an RIE process because it requires a relatively slow etch rate and low selectivity, both could not be obtained by DRIE. According to the photoresist thickness developed in the gray scale lithography, an RIE process with a selectivity of 0.55 was required. We implement the DOE (design of experiment) method for finding the process parameters which gives the desirable selectivity and its tolerance which is crucial for determining the range of the Fresnel lens height. It was found that according to the selectivity tolerance, the Fresnel lens stands within ±10% tolerance of its height. Finally, we demonstrated the imaging of an object using the 600 nm lens.
Nanofabrication II: Growth and Deposition
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An evaporative co-assembly method for highly ordered inverse opal films
Benjamin Hatton, Lidiya Mishchenko, Robert Norwood, et al.
Colloidal self-assembly holds promise for photonic applications as a solution-based, low-cost alternative to top-down photolithography, if significant control of uniformity and defects can be achieved. Herein we demonstrate a new evaporative co-assembly method for highly-uniform inverse opal thin films that involves the self-assembly of polymer colloids in a solution containing a silicate precursor. Nanoporous inverse opal films can be made crack-free and with highly uniform orientation at the cm scale. The silicate between the colloids appears to increase the strength against cracking. This control of defects makes this method well-suited for the low cost fabrication of such films as sensors and photonic devices.
Microlithographically patterned optical thin film coatings
Jim Lane, Phil Buchsbaum, Jason M. Eichenholz
Until recently optical coatings have been one area that existed primarily in the macro realm. Entire optical surfaces could be coated quite easily with various thin film optical coatings. However precise deposition of patterned optical filter coatings was limited by the use of metal masking. Similarly, the dicing and bonding of individual filters together to form an assembly is a tedious process, with miniaturization limited by handling and dicing constraints. We are reporting on a new class of lithographically patterned dielectric thin film coatings that enables precision placement and patterning of dichroic and multilayer thin film coating features on a single substrate down to the micron scale. Because the process relies on precision microlithography instead of cut metal masks to pattern the deposited coatings, features (coated areas) as small as 5 microns can be produced, with spatial registration to adjacent coated areas within 1 micron. Furthermore, we report on new developments which involve patterning optical thin film filter on active photodetector substrates. The possibility of now using active devices with patterned dielectric optical filter arrays opens up a wide landscape of new opportunities in solid-state spectral sensing, from more precise color detection to enhanced multispectral imaging.
3-D Nanofabrication
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Metallodielectric 3D photonic crystals prepared by metallization of optically microfabricated polymeric templates
Vygantas Mizeikis, Rima Tarozaite, Saulius Juodkazis, et al.
Metallodielectric photonic crystals (MDPC) were fabricated by the combination of direct laser writing technique, which was used to prepare initial dielectric templates, and by subsequent metalization of the templates using electroless coating technique. The obtained MDPC structures have adequate structural quality, and exhibit spectral signatures of photonic bands consistent with theoretical expectations. The fabrication process is simple but reliable, and can deliver MDPC structures suitable for operation in the infrared and terahertz spectral ranges.
Fabrication of large area woodpile structure in polymer
A fabrication process of three-dimensional Woodpile photonic crystals based on multilayer photolithography from commercially available photo resist SU8 have been demonstrated. A 6-layer, 2 mm × 2mm woodpile has been fabricated. Different factors that influence the spin thickness on multiple resist application have been studied. The fabrication method used removes, the problem of intermixing, and is more repeatable and robust than the multilayer fabrication techniques for three dimensional photonic crystal structures that have been previously reported. Each layer is developed before next layer photo resist spin, instead of developing the whole structure in the final step as used in multilayer process. The desired thickness for each layer is achieved by the calibration of spin speed and use of different photo resist compositions. Deep UV exposure confinement has been the defining parameter in this process. Layer uniformity for every layer is independent of the previous developed layers and depends on the photo resist planarizing capability, spin parameters and baking conditions. The intermixing problem, which results from the previous layers left uncrossed linked photo resist, is completely removed in this process as the previous layers are fully developed, avoiding any intermixing between the newly spun and previous layers. Also this process gives the freedom to redo every spin any number of times without affecting the previously made structure, which is not possible in other multilayer process where intermediate developing is not performed.
Applications
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Advances in diffractive nanophotonics enabled by commercial photoreduction lithography
Christoph M. Greiner, Dmitri Iazikov, Thomas W. Mossberg
We describe monolithic advanced-function diffraction grating arrays for instantaneous ultrawide spectral coverage and other uses that have inherent spectral and spatial self-calibration features. This new technology is made possible by recent advances in deep ultraviolet (DUV) reduction-lithographic fabrication.
Fabrication of diffractive optics for dense optical interconnects in optical computing
A. A. Cruz-Cabrera, S. A. Kemme, J. R. Wendt, et al.
We designed and fabricated an optical system containing high efficiency diffractive optical elements (DOEs) with large numerical apertures (NA) for an all-optical gate, based on a Symmetric Self-Electro-Optic Effect Device (S-SEED) technology. The S-SEEDs are the active elements that perform the optical switching in the optical interconnect. Multiple, off-axis DOEs are used to collect and focus light onto the S-SEEDs and the Input/Output optical fibers. Each S-SEED has at least seven input signals, two alignment signals, and two output signals. Each signal uses a DOE. DOE fabrication is relatively mature and utilizes the precise lateral alignment inherent in photolithography to produce arrays compatible with dense optical interconnects. Losses across the system have a negative impact on the S-SEED switching speeds. The primary challenge of DOEs is the diffractive optic efficiency that corresponds to high NAs. Lower efficiencies, due to requirements for large deflection angles, lead to extremely small feature sizes in the outer zones of the DOEs. We optimize DOE efficiency with modifications to the blaze geometry and by selecting the appropriate number of levels for specific deflection angles. The system layout is modified to reduce complexity by working in collimated space between the S-SEEDs instead of imaging onto relay mirrors. This reduces the spatial frequency of the DOEs and increases system tolerance by not imaging mirror defects. Finally, we quantify the effects of lithographic masks misalignment and look at the step geometry deviations and their effects on DOE efficiency.
Diffraction gratings for compact integrated optical structures
Diffraction gratings used in various applications for compact optical devices. We used different technologies for this task: deep-UV lithography, FIB milling, e-beam lithography, and hot embossing/nanoimprinting technology. We analyzed advantages and disadvantages of each fabrication technology.
Nanofabrication III: Metallic Nanostructures and Plasmonics
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Nanoskiving: a novel method for nanofabrication and its applications in nanophotonics
Qiaobing Xu, George M. Whitesides
Nanoskiving is a novel and inexpensive method that has been used to fabricate both isolated nanostructures and ordered arrays of nanostructures. The dimensions of the nanostructures are determined by i) the thickness of the deposited thinfilm (tens of nanometers), ii) the topography (sub-μm, using soft lithography) of the surface onto which the thin-film is deposited, and iii) the thickness of the section cut by the microtome (> 30 nm by ultramicrotomy). Nanoskiving can fabricate complex nanostructures that are difficult or impossible to achieve by other methods of nanofabrication. These include multilayer structures, structures on curved surfaces, structures that span gaps, structures in less familiar materials, structures with high aspect ratios, and large-area structures comprising two-dimensional periodic arrays. In this paper, we described the history, procedure, and applications, particularly in nanophotonics, of nanoskiving.
Fabrication of surface plasmon resonators by nanoskiving single-crystalline gold microplates
Benjamin J. Wiley, Darren J. Lipomi, Jiming Bao, et al.
This paper demonstrates the sectioning of chemically synthesized, single-crystalline microplates of gold with an ultramicrotome to produce single-crystalline nanowires. This method produces collinearly aligned nanostructures with small, regular changes in dimension with each consecutive cross-section. The diamond knife cuts cleanly through microplates 100 nm thick without bending the resulting nanowire, and cuts through the sharp edges of a crystal to generate nanoscale tips. This paper demonstrates that the smooth surface of the single-crystalline gold nanowires allows them to guide plasmons with lower loss than rough, polycrystalline nanowires, and that the sharp tips on the singlecrystalline nanowires serve as optical antenna that selectively couple light into the nanowire at the resonance frequency of the sharp tip.
E-beam assisted fabrication of a subwavelength aluminum mesh
Clarisse Mazuir, J. Thomas Deng, Jim C. M. Hwang, et al.
Using e-beam lithography on a single layer of polymethylmethacrylate (PMMA) we designed a relatively thick subwavelength aluminum mesh on top of sapphire. The 100 nm thick mesh consisted of two perpendicularly oriented sets of 100 nm wide parallel metal lines with a center to center distance as low as 260 nm. Due to the large proximity effect during e-beam exposure and the small spacing between metallic lines the use of an adhesion promoting layer appeared necessary to avoid premature peeling of the photoresist. Using a monoatomic layer of hexamethyldisilazane (HMDS) as an adhesion promoter between the sapphire and the PMMA, a 500 nm thick photoresist layer could be exposed and developed with excellent control over the features sizes. Line spacing distances from 500 nm down to 160 nm were achieved. An oxide plasma etch was found to be necessary for metal adhesion during the lift-off process. Due to the small spacing between the aluminum lines, use of a bi-layer photoresist technique to achieve undercut was not possible. Thermal evaporation of aluminum was performed and e-beam evaporation didn't help smoothing the metal surface. An additional ultrasonic bath in acetone was found necessary to ease the lift-off process.
Fabrication of novel plasmonics-active substrates
Anuj Dhawan, Michael Gerhold, Yan Du, et al.
This paper describes methodologies for fabricating of highly efficient plasmonics-active SERS substrates - having metallic nanowire structures with pointed geometries and sub-5 nm gap between the metallic nanowires enabling concentration of high EM fields in these regions - on a wafer-scale by a reproducible process that is compatible with large-scale development of these substrates. Excitation of surface plasmons in these nanowire structures leads to substantial enhancement in the Raman scattering signal obtained from molecules lying in the vicinity of the nanostructure surface. The methodologies employed included metallic coating of silicon nanowires fabricated by employing deep UV lithography as well as controlled growth of silicon germanium on silicon nanostructures to form diamond-shaped nanowire structures followed by metallic coating. These SERS substrates were employed for detecting chemical and biological molecules of interest. In order to characterize the SERS substrates developed in this work, we obtained SERS signals from molecules such as p-mercaptobenzoic acid (pMBA) and cresyl fast violet (CFV) attached to or adsorbed on the metal-coated SERS substrates. It was observed that both gold-coated triangular shaped nanowire substrates as well as gold-coated diamond shaped nanowire substrates provided very high SERS signals for the nanowires having sub-15 nm gaps and that the SERS signal depends on the closest spacing between the metal-coated silicon and silicon germanium nanowires. SERS substrates developed by the different processes were also employed for detection of biological molecules such as DPA (Dipicolinic Acid), an excellent marker for spores of bacteria such as Anthrax.
Micro- and Nanoreplication
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Roll-to-roll manufacturing of subwavelength optics
Vivian W. Jones, Silva Theiss, Mark Gardiner, et al.
Over the years there have been demonstrations of various methods capable of forming sub-micron features such as photo, electron beam, and imprint lithography. Generally these methods are limited to planar master tools of limited dimensional size. The subsequent replication processes using these master tools are typically a batch or a rollto- roll process with a tiled master roll tool. Presented here is a novel method for the large scale manufacturing of sub-micron structures via a roll-based mastering method suitable for industrial scale, based on a modification of single point diamond turning. Single point diamond turning has been exploited successfully to generate a wide range of optical structures from discrete optical components to large area micro-optic based films such as brightness enhancement films (BEF) for LCD displays. By applying advanced ion-milling techniques to structure diamond tools, it is possible to increase the complexity and ultimate dimensional resolution of diamond machined masters.
High-speed roll-to-roll nanoimprint lithography on flexible substrate and mold-separation analysis
Se Hyun Ahn, L. Jay Guo
Continuous Roll-to-Roll NanoImprint Lithography (R2RNIL) provides greatly improved throughput by overcoming the challenges faced by conventional NIL in maintaining pressure uniformity and successful large-area imprinting and demolding. We present continuous imprinting of nanoscale structures with linewidth down to 70nm on a flexible plastic substrate. Our new process used a flexible and non-sticking fluoropolymer mold, and fast thermal and UV curable liquid resist materials. In addition, pattern quality in continuous R2RNIL process according to two different mold-separation directions has been analytically investigated.
Ultrafast response of negative index metamaterials in the near-infrared
Nanoimprint lithography is used to fabricate a metamaterial with the "fishnet" structure composed of Ag/a-Si/Ag layers that exhibits negative refractive index in the near-infrared. We have carried out a femtosecond pump-probe experiment to measure the transient photo-induced response of this structure. With a pump fluence of 330μJ/cm2 at 800nm, the transmission at the magnetic resonance is increased by ~15.4%. The induced change originated from carrier excitation in the a-Si layer has a fast decay constant of 1.1ps.
Advanced Lithography
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Correlation of fabrication tolerances with the performance of guided-mode-resonance micro-optical components
Large-scale fabrication of micro-optical Guided-Mode-Resonance (GMR) components using VLSI techniques is desirable, due to the planar system integration capabilities it enables, especially with laser resonator technology. However, GMR performance is dependent on within-wafer as well as wafer-to-wafer lithographic process variability, and pattern transfer fidelity of the final component in the substrate. The fabrication of lithographs below the g-line stepper resolution limit is addressed using multiple patterning. We report results from computational simulations, fabrication and optical reflectance measurements of GMR mirrors and filters (designed to perform around the wavelength of 1550nm), with correlations to lithographic parameter variability, such as photoresist exposure range and etch depth. The dependence of the GMR resonance peak wavelength, peak bandwidth are analyzed as a function of photolithographic fabrication tolerances and process window.
Laser-based Fabrication for Photonics
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In-volume waveguides by fs-laser direct writing in rare-earth-doped fluoride glass and phosphate glass
D. Esser, D. Wortmann, J. Gottmann
Refractive index modifications are fabricated in the volume of rare-earth-doped glass materials namely Er- and Pr-doped ZBLAN (a fluoride glass consisting of ZrF4, BaF2, LaF3, AlF3, NaF), an Er-doped nano-crystalline glass-ceramic and Yb- and Er-doped phosphate glass IOG. Femtosecond laser radiation (τ=500fs, λ=1045nm, f=0.1-5MHz) from an Ybfiber laser is focused with a microscope objective in the volume of the glass materials and scanned below the surface with different scan velocities and pulse energies. Non-linear absorption processes like multiphoton- and avalanche absorption lead to localized density changes and the formation of color centers. The refractive index change is localized to the focal volume of the laser radiation and therefore, a precise control of the modified volume is possible. The width of the written structures is analyzed by transmission light microscopy and additionally with the quantitative phase microscopy (QPm) software to determine the refractive index distribution perpendicular to a waveguide. Structures larger than 50μm in width are generated at high repetition rates due to heat accumulation effects. In addition, the fabricated waveguides are investigated by far-field measurements of the guided light to determine their numerical apertures. Using interference microscopy the refractive index distribution of waveguide cross-sections in phosphate glass IOG is determined. Several regions with an alternating refractive index change are observed whose size depend on the applied pulse energies and scan velocities.
Demonstration of inscription and ablation of phase masks for the production of 1st, 2nd, and 3rd order FBG gratings using a femtosecond laser
Graham N. Smith, Kyriacos Kalli, Ian Bennion, et al.
We present to the best of our knowledge the first example of femtosecond laser inscription/ablation of phase/amplitude masks for the demonstrated purpose of inscribing Bragg gratings in optical fibers. We show that the utilization of a femtosecond laser for the mask production allows for great flexibility in controlling the mask period. The masks are used to produce 1st, 2nd and 3rd order fiber Bragg gratings (FBGs) in SMF-28. The work demonstrates the proof of concept and flexibility for the use of femtosecond lasers for the rapid prototyping of complex and reproducible mask structures. Our inscription studies are augmented by considerations of three-beam interference effects that occur as a result of the strong zeroth-order component that is present in addition to higher-order diffraction components.
Dynamic ultrafast laser beam tailoring for multispot photo-inscription of photonic devices in bulk transparent materials
C. Mauclair, G. Cheng, N. Huot, et al.
Femtosecond laser processing of bulk transparent materials can generate localized increase of the refractive index. Thus, translation of the laser spot give potential access to three dimensionnal photowriting of waveguiding structures. Increasing the number of machining foci can considerably reduce the processing efforts when complex photonic structures are envisaged such as waveguide arrays. The present report presents a technique of dynamic ultrafast laser beam spatial tailoring for parallel writing of photonic devices. The wavefront of the beam is modulated by a periodical binary (0-π) phase mask of variable pattern to achieve dynamic multispot operation. The parallel photoinscription of multiple waveguides is demonstrated in fused silica. Using this method, light dividers in three dimensions relying on evanescent coupling are reported and wavelength-division demultiplexing (WDD) devices were achieved in single sample scan.
Microfabrication of refractive optics, waveguides, microfluidics, and high-aspect ratio structures realized by direct laser lithography
Pierre Blanchet, Cécile Aubert, Nicolas Brillouet, et al.
Microlens, micromirrors, quantum dots and microfluidics networks are some elements illustrating the need of miniaturisation for optics. This paper presents examples of high aspect ratio microstructures obtained with Dilase technology, a direct laser lithography technique in photosensitive layers. Vectorial writing associated with specific laser beam treatment allows imagine fast prototyping and production of a large range of MOE. Integrated optical circuits, such as optical MUX/DEMUX and splitters are strongly used in telecommunication and sensors industries. Microlens arrays, micromirrors present a large potential for imagery sector. "Lab on a chip" integrating microfluidic and optical waveguides systems are useful for medical diagnosis.
Poster Session
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Fabrication of two-layer diffractive optical element for single-beam and single-exposure fabrication of diamond-like photonic crystal
Yuankun Lin, Ahmad Harb, Daniel Rodriguez, et al.
We report a new design and fabrication of an integrated two-layer phase mask for five-beam holographic fabrication of three-dimensional photonic crystal templates. The fabricated phase mask consists of two layers of orthogonally oriented gratings produced in a polymer. The vertical spatial separation between two layers produces a phase difference among diffractive laser beams, which has enabled a holographic fabrication of diamond-like photonic crystal templates through single-beam and single-exposure process. The reported method simplifies the fabrication of photonic crystals and is amendable for massive production and chip-scale integration of three-dimensional photonic structures.
Characterization of hybrid molding and lithography for SU-8 micro-optical components
SU-8 is a very promising material for micro-optics. It is mechanically robust with high thermal and chemical resistance, has high transmission at visible and near-infrared wavelengths, and has relatively high refractive index after curing. While lithographic processing of SU-8 is relatively common, molding of SU-8 requires different processing parameters due to challenges with solvent removal and cross linking. Understanding the effects of the molding process on SU-8 is necessary to optimize performance of molded micro-optical components, and also to enable fabrication of more complex micro-optics through subsequent lithographic processing of molded structures. In this paper, we examine properties of SU-8 as it undergoes the molding process. General characterization of SU-8 shrinkage/expansion is presented, and minimum moldable feature sizes are explored. Solvent content and refractive index as functions of processing parameters are also examined, along with analysis of the SU-8's lithographic properties after undergoing the molding process. These characterizations further enable hybrid combinations of micro-molding and lithographic processing to fabricate complex micro-optics that are difficult or impossible to realize using conventional techniques.